Transcript for New Clues May Provide Information on Boston Marathon Bombing

-- shows us just how far the blast from the bombs travel. -- The killer bombs likely contain less than two pounds of common black powder explosive. Says one of the nation's leading IED experts even leaving the characteristic white smoke. Bombs designed to spread terror and death with a lethal blast a metal shrapnel. It looks like he was to kill -- -- -- right there. Good so here we see. Windows blown out here but the buildings themselves. Are intact what is all that tell us. About what this bomber wanted to do but he did not want to take down the buildings that wasn't his main target it was to disrupt the marathon and kill people in that immediate area. Houston says this is classic IED designed. The fatal zone from the blast just one -- two yards but according to accounts from the bomb site powerful enough to -- a runner off his feet ten yards away. And topple another man from his couch in the third floor of the building next door twenty yards away. It looks like it's pretty basic design of an improvised explosive device however the placement is -- sophisticated. They understood what they wanted to do and when they wanted to do it. The pressure -- is well known by the military -- a lethal bomb carrier covered in their training manuals and displayed in action in video. -- IED's may be small easily made it even crew. But our bomb expert says the planning and execution tell him that the terrorist was well trained. I would be surprised. And if it's alone -- Definitely been working on this for a while the planning. And working on putting the devices together but none of the clues so far tell our expert whether this terrorist was part of any one organization.

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